Post-mix beverage dispensers combine carbonated water with a concentrated beverage syrup to provide a final beverage for dispensing and consumption. The beverage syrup, which is often a dense and/or viscous fluid, is typically supplied from a bag-in-box syrup container. A syrup pump may be used to move the syrup from the syrup container to the dispensing nozzle.
Conventionally, this syrup pump is a diaphragm-type pump, which is driven by a compressed gas source. In many instances, the compressed gas source may be compressed carbon dioxide, which is also used for preparing the carbonated water. Syrup pumps of this type have at least two disadvantages. First, the pumps use rubber diaphragms which come in contact with the syrup being pumped and quickly absorb flavors from the syrup, and these flavors may subsequently be leached outed into other fluids which later pass through the pump. Thus once the diaphragms in a pump become saturated with the flavor of a given syrup, the pump cannot be repurposed to pump a different flavored beverage without having a detrimental effect on the flavor the new beverage. The pump becomes effectively dedicated to a single flavor of beverage syrup.
Secondly, and more significantly, gas driven diaphragm pumps are prone to leakage of the compressed gas used to drive the pump. Again, in post-mix beverage dispensers, this gas is typically carbon dioxide, which is colorless, odorless, and which presents an asphyxiation hazard in confined spaces.
Accordingly, what is desired is an improved syrup pump for a beverage dispenser which would eliminate the problem of flavor cross-contamination when pumps are repurposed for different flavored beverages. It is also desired to provide a syrup pump for a beverage dispenser which would eliminate the asphyxiation hazard associated with the use of compressed carbon dioxide or other inert gases.